The present invention relates to rotary drum mixers for mixing dry particulate matter and, in particular, it relates to reducing assemblies for reducing the size of a product being mixed in a rotary drum mixer.
Rotary drum mixers for mixing product matter in particulate form are known in the art. Rotary drum mixers typically include a rotatable open-ended drum and a stationary hopper positioned on or adjacent the mixer for introducing product matter into the drum. The drum includes front inclined troughs for directing the product matter in a direction away from the open end and rear inclined troughs for directing product matter in the opposite direction. The multi-directional troughs mix the product matter to a desired blend as the drum rotates.
Generally, a stationary hood encloses the drum open end and turbine blades fixedly attached to the drum elevate product matter within the stationary hood. The turbine blades direct the product matter to a discharge hopper mounted on the hood. A seal member between an annular flange on the stationary hood abuts against the outside of the rotating drum. Such rotary drum mixers are illustrated, for example, in U.S. Pat. Nos. 3,552,721 and 3,897,934.
There are times when a rotary drum mixer user desires to mix product matter, then have the particulate material of the product matter reduced in size and then again mix the reduced-size particulate material. In order to accomplish such a task, the rotary drum mixer is loaded with the original product matter, operated until all product matter is mixed to a desired blend and then emptied. The mixed product matter is then transported either within or outside the mixing facility to a device, such as a crushing mill or roll, which can accomplish the particulate size reduction. Then, the size-reduced product matter is transported back to the mixing facility, loaded into the mixer and mixed until the desired blend is once again accomplished. Such a time intensive process as described above results in increased expenditures in the form of increased labor, lower productivity and increased plant size due to need for additional machinery, and also requires additional handling and enhances the possibility of contamination of the product matter.
In the Phillips U.S. Pat. No. 3,829,066, a particulate material mixing machine is described. Instead of the multi-directional troughs as described above, the mixing machine of the Phillips '066 patent describes an auger-type assembly mounted entirely within the drum and having a housing, a rotating spiral blade for moving product matter through the housing and a rotating fan to fling the product matter rearwardly to descend into the drum substantially throughout the axial length thereof. While the spiral blade can include extending lugs to help break up chunks and clumps of product matter within the housing, the spiral blade does not uniformly reduce the particulate size of the product matter being mixed. The stated object of the Phillips '066 patent disclosure is to increase the speed that product matter is mixed.